1. Field of the invention
The present invention relates to a motor control system having a clamp function and method thereof for controlling a motor apparatus.
2. Description of the Prior Art
The motor control system of the prior art comprises a motor controller for controlling the operation of a motor apparatus. The motor controller generates a motor control output according to a feedback signal from the motor apparatus. However, damages on the disc surface above the spindle motor and external disturbances might all influence the feedback signal, thus causing abnormal motor control output and resulting in stability problem.
To solve the stability problem, the prior art limits the motor control output to be in a specific range or fixes the output in different conditions. Although these methods may avoid unknown disturbance to influence the motor, they will also influence the motor control output while the motor apparatus is in the normal state.
In U.S. Pat. No. 5,161,141, the optical information recording/reproducing system clamps the control voltage in a specific range. However, if the above method is applied to control the spindle motor, the normal control voltage will be limited in the clamp range while tracking normally, thus not capable of reflecting correct results.